The purpose of this study is to evaluate the cooling efficiency of a low-temperature micro-mist system in an open roof greenhouse. For traditional blast spray cooling system, a fan is paired with ambient fine spray,where the spray volume and the effect of humidity in that environment are crucial. However, it was unable to lower the water temperature mostly, thus cooling has not beenparticularly created in the greenhouse facilities. In thisstudy, temperature and humidity in the greenhouse canbe effectively controlled and adjusted by using an airconditioning system with cooling fog created with spraynozzles at 100 kgf/cm2 which spewed low temperature (10℃) micro mist. With the hot-air-up and cool-air-down principle, the facility could discharge the air at high temperature and high humidity, thus creating the cooling effect. Experimental results showed that when the outdoor temperature was 28.2℃ at 12:00, the ORG1greenhouse without any cooling equipment couldcumulate solar radiation and heat to the maximum extent,and thehighest temperature for the day was 42.3℃. Inthe meantime, the ORG2 greenhouse under the effect of low-temperature micro-mist cooling system, the temperature was kept at 22.2℃ and the humidity was 72.8%. The cooling effect expressed in temperature reduction was more than 20℃. The micro-mist cooling system was thus proved to be capable of reducing the temperature inside the greenhouse dramatically.